(1) Field of the Invention
The present invention relates to a laminated photosensitive material and a process for the production thereof. More particularly, the present invention relates to an improvement of a laminated photosensitive material comprising an electroconductive substrate, a charge-generating layer formed on the substrate by vacuum deposition of metal-free phthalocyanine and a charge-transporting layer formed on the charge-generating layer, wherein the charge quantity of the photosensitive material is increased and the electrophotographic characteristics at the time of repeated or continuous use are stabilized.
(2) Description of the Prior Art
A function-separated type electrophotographic photosensitive material comprising a charge-generating layer formed on a electroconductive substrate and a charge-transporting layer formed on the charge-generating layer has attracted attention as an organic photosensitive material excellent in electrophotographic characteristics such as the sensitivity. As the charge-generating layer of the photosensitive material of this type, various organic photoconductive pigments have been vacuum-deposited on substrates or resin dispersions of these pigments have been coated as substrates. Among these organic photoconductive pigments, metal-free phthalocyanine is stable against light, heat and discharge and has a sensitivity to longer wavelengths. Accordingly, researches have been made with a view to using metal-free phthalocyanine for a charge-generating layer.
When the vacuum deposition treatment metal-free phthalocyanine is carried out at a relatively low temperature, an .alpha.-form crystal is formed, and if the treatment is carried out at a relatively high temperature a vacuum deposition film composed mainly of a .beta.-form crystal is formed. The dark conductivity of a vacuum deposition film of an .alpha.-form crystal is as high as 10.sup.-6 to 10.sup.-7 (.OMEGA.-cm).sup.-1, and the film is defective in that if a laminated photosensitive plate provided with this vacuum deposition film is used for the electrophotography, the initial charge voltage is relatively low and if the electrophotographic operation is repeated, the initial charge voltage is abruptly reduced.